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Cord Blood Gas Results | What You Need to Know

Cord blood gas analysis determines the fetal metabolic condition when umbilical circulation stops during childbirth. 

Clamping the umbilical cord is standard procedure when a baby is born.  Studies have shown this is a vital component to determining the health of your baby. 

Umbilical cord blood gas analysis helps doctors can detect if the child suffered a birth injury during delivery. Cord blood gases show whether or not a baby is experiencing acidosis, which can indicate that there was a hypoxic-ischemic event

The results from cord blood gases are frequently used as evidence in medical malpractice lawsuits by both attorneys and doctors as a marker for the harm done to the child and to prove whether negligence was involved in a child's injury.  

When our birth injury lawyers are discussing a new case that has come into our office, one of the first questions is about the child's cord blood gas values.  But you do not need to have a malpractice lawsuit to want to better understand your child's blood gas values and what they mean. 

What Are Cord Blood Gases?

To understand what cord blood gases are, it's helpful to know how the placenta supplies oxygen and nutrition to a baby in the womb. A fetus relies on the mother for oxygen and carbon dioxide exchange. A developing baby does not breathe in the same way they would after birth. 

The placenta uses gas exchange to supply them with oxygen that comes from the mother's blood. After the mother's blood is oxygenated, it is absorbed by the placenta's capillaries. 

The capillaries will then deliver the blood to the placenta's main artery where it is finally transferred to the baby.

Why Are Core Blood Gases Important to Access a Newborn?

When the baby is born, the umbilical artery briefly retains information about the baby's current condition, referred to as blood cord gases. Doctors clamp the umbilical cord within seconds after birth to be able to measure the level of acidity inside the umbilical artery.

The question is how much oxygen the baby was getting.  Analyzing cord blood gas levels is often the best indicator of hypoxia or ischemia during the delivery period.

The results of the analysis can show how healthy the baby is and determine if they have a birth injury.

It is also important to get accurate results. This is why the cord must be clamped quickly. Waiting even 45 seconds will skew the results due to chemicals changing in the artery.

What Is Base Excess?

The base deficit is calculated using measured blood levels for acid (pH), dissolved carbon dioxide gas (PCO2), and bicarbonate HCO. It is these values that describe the baby's metabolic state.

How Do You Draw Umbilical Cord Blood?

The doctor will clamp the umbilical cord quickly after childbirth. A needle withdraws blood that is in the cord. Again, this needs to be done quickly to get reliable umbilical cord blood gas results.

How Are Blood Cord Gases Measured?

The most important measurements used in arterial cord blood gases examination are the baby's pH levels and their base deficit. Both are used to determine the acidity level in the umbilical cord. 

The levels determine if the baby has acidosis, a condition caused by the overproduction of acid in the blood. Acidosis usually presents itself as decreased blood pH and increased base deficit. If a baby has acidosis, you will see poor cord gases at birth.  It is a red flag that indicates the presence of hypoxia during delivery.

What Are Normal Arterial Blood Gases Values?

Normal arterial blood cord gases values in a full-term newborn:

  • Mean pH: 7.28 ± 0.07
  • Mean PCO2 (carbon dioxide): 49.9 ± 14.2 (mmHg)
  • Mean PO2 (oxygen): 23.7 ± 10.0 (mmol/L)
  • Mean base deficit: -3.6 ± 2.8 (mmol/L)

Normal blood cord gases levels in a preterm newborn:

  • Mean pH: 7.29 ± 0.07
  • Mean PCO2: 49.2 ± 9.0 (mmHg)
  • Mean PO2: 23.6 ± 8.9 (mmol/L)
  • Mean base deficit: -3.3 ± 2.4 (mmol/L)

Cord Blood Gases InfographicAll values are ± 1 standard deviation. The "P" in PO2 and PCO2 means "partial pressure", which is how the cord blood gases are measured. PCO2 measures the amount of carbon dioxide gas dissolved in the blood, and PO2 measures how much oxygen is in the blood.

Why Are PH Levels Important?

Cord pH provides an important measurement of the acid-base status of the baby at the moment that the cord was cut. This gives a good window into the oxygenation status of the fetus in the immediate period leading up to delivery.

How Does Acidosis Affect My Baby?

Acidosis has two different types: respiratory acidosis and metabolic acidosis. Respiratory acidosis refers to high acid levels caused by impaired lung function, leading to retained carbon dioxide in the lungs and bloodstream. 

Metabolic acidosis is when there are high acid levels in the body that originated from impaired kidney function. Both forms of acidosis can cause neurological issues that can be temporary or permanent depending on how severe the damage is. In general, however, metabolic acidosis is associated with more adverse outcomes.

Low pH levels caused by acidosis can result in hypoxic-ischemic encephalopathy, periventricular leukomalacia, seizures, brain hemorrhages, and cerebral palsy. In severe cases of metabolic acidosis, it can lead to multi-organ failure and even death. 

The primary cause of acidosis comes from the lack of adequate oxygen being transferred from the placenta to the baby.

Blood Cord Gases in Lawsuits

Blood cord gases results can be used as an important piece of evidence in birth injury litigation. If a baby suffered from hypoxia that resulted in a birth injury, the blood cord gases can prove the legitimacy of the plaintiff's claim. 

The interpretation of blood cord gas levels can also be used by malpractice lawyers and medical experts to show the severity of damage that occurred during delivery by citing the specific pH and base deficit levels. 

However, doctors can also use blood cord gases to defend birth injury lawsuits as well.  If the baby has a birth injury but their blood cord gases came back normal, the obstetrician can use the umbilical cord gas levels as evidence that the injury did not occur during delivery and was not caused by negligence.

There are many reasons as to why a baby would have normal blood cord gases despite suffering from a hypoxic brain injury. The baby might have had poor circulation and perfusion shortly before being born or they could have experienced a physical head injury during delivery. 

There may have been an error in the process of storing and analyzing the blood. According to one study, up to 19% of blood cord gas samples are invalid due to human error. There are also blood cord gas interpretation errors that inflate or deflate the child's hypoxia at birth. 

To prevail in a birth injury lawsuit involving blood cord gases, a medical malpractice attorney needs to be skilled in their medical knowledge about pH and base deficit levels. 

They should take the time to examine the process of taking blood cord gas samples and identify any possible technical errors that make the results invalid. Birth injury lawyers also need to work closely with a medical expert to prove the cause and timing of the birth injury.

Do Abnormal Cord Blood Gases Mean My Child Has a Brain Injury?

Abnormal cord blood gas results are a marker for a birth injury.  But abnormal fetal cord blood gas results do not mean that your child has a brain injury. Many children with troubling cord blood gas and APGAR results and have no long-term physical or cognitive deficits.

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